Fracture behaviors of concrete incorporating different levels of recycled coarse aggregate after exposure to elevated temperatures

Abstract This study focuses on the fracture behavior of recycled aggregate concrete (RAC) after exposure to elevated temperatures, thus, a total of 128 cubic specimens and 64 notched beams were cast to analysis the effects of recycled coarse aggregate (RA) substitutions (0%, 30%, 70% and 100%) and elevated temperatures (20 °C, 100 °C, 200 °C and 300 °C) on fracture parameters of RAC, such as peak load (Pmax), critical crack mouth opening displacement (CMODc), critical crack tip opening displacement (CTODc), effective crack length (ac), fracture energy (GF), initiation fracture toughness ( K I C i n i ) , unstable fracture toughness ( K I C u n ), the characteristic length (Lch) and so on. The result showed that the values of Pmax decreased as the increase of exposure temperature and the decrease rate grew slower as the increase of RA substitution. In contrast, the values of GF increased with elevated temperature and the increased rate grew slow with the incremental of RA replacement. As the increase of RA substitution, the CMODc and CTODc of specimens slightly increased first and then decreased at ordinary temperature and elevated temperature. The K I C i n i and K I C u n of concrete with different RA substitution decreased with the elevated temperatures. In addition, the RA substitution had a positive impact on the K I C i n i of concrete after exposure to 200 °C and 300 °C. At each high temperature, the Lch of RAC was smaller than that of natural aggregate concrete (NAC), indicating that the ductility of RAC was worse than that of NAC.